Did you check all IP addresses and see whether or not they are correct as expected?

I believe it is a security issue. You may not have authority to read the idc file or access the database. Here is a link. May it help.

http://support.microsoft.com/kb/q161172/

Did you change your link string accordingly?

You talked about node. Did you build your SQL Server on a cluster? A node is different from a name of an SQL Server on a cluster.

Ask your DBAs what they did recently, such as linked server.

Could you provide the differences in hardware configurations?

I would like to guess some other processes were running on your server when differential backups started. These processes may locks the database from backup. Could you monitor other jobs...

They are syntax errors from my point of view. Try to use [] to enclose your database name, and see what will happen.

If you fire your job from VB, you can add ON ERROR RESUME NEXT clause.

Here is a link. May it help.

http://support.microsoft.com/kb/834124

Here is a link. May it help.

http://markiehill.blogspot.com/2005/08/moving-cube-directories-in-sql-server.html

Here is a link. May it help.

http://tutorials.aspfaq.com/8000xxxxx-errors/80004005-errors.html

Could you SELECT TOP ... when creating your cursor?

Corruption of the backup file is one of possible reasons. I got the same error once restoring a database. I pinned the error was the corruption of the backup file...

Did you check whether or not the backup file was in use when the deletion failed?

You may add a log file in your database maintenance plan to obtain information in...